From 5f4011ef2969e4c4ac93f570bef45e9afb65bb9a Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Wed, 9 Oct 2013 13:10:28 +0200
Subject: [backport] SI-7902 Fix spurious kind error due to an unitialized
 symbol

Tracked down this error:

    <none> is invariant, but type Y2 is declared covariant
    <none>'s bounds<notype> are stricter than type X2's declared bounds >: Nothing <: Any, <none>'s bounds<notype> are stricter than type Y2's declared bounds >: Nothing <: Any

to `Symbol#typeParams` returning `List(NoSymbol)` if the symbol
was not initialized.

This happends in the enclosed test for:

    // checkKindBoundsHK()
    hkArgs   = List(type M3)
    hkParams = List(type M2)

This commit forces the symbol of the higher-kinded type argument
before checking kind conformance.

A little backstory:

The `List(NoSymbol)` arises from:

    class PolyTypeCompleter... {
      // @M. If `owner` is an abstract type member, `typeParams` are all NoSymbol (see comment in `completerOf`),
      // otherwise, the non-skolemized (external) type parameter symbols
      override val typeParams = tparams map (_.symbol)

The variation that triggers this problem gets into the kind
conformance checks quite early on, during naming of:

    private[this] val x = ofType[InSeq]

The inferred type of which is forced during:

    def addDerivedTrees(typer: Typer, stat: Tree): List[Tree] = stat match {
      case vd @ ValDef(mods, name, tpt, rhs) if !noFinishGetterSetter(vd) =>
        // If we don't save the annotations, they seem to wander off.
        val annotations = stat.symbol.initialize.annotations

(cherry picked from commit 03a06e02483eaf442158339c2edd6bcfd99847a3)
---
 test/files/pos/t7902.scala | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 test/files/pos/t7902.scala

(limited to 'test/files/pos/t7902.scala')

diff --git a/test/files/pos/t7902.scala b/test/files/pos/t7902.scala
new file mode 100644
index 0000000000..47c525c179
--- /dev/null
+++ b/test/files/pos/t7902.scala
@@ -0,0 +1,17 @@
+import scala.language.higherKinds
+
+object Bug {
+  class Tag[W[M1[X1]]]
+
+  def ofType[W[M2[X2]]]: Tag[W] = ???
+  type InSeq  [M3[X3]] = Some[M3[Any]]
+
+  // fail
+  val x = ofType[InSeq]
+
+  // okay
+  val y: Any = ofType[InSeq]
+  object T {
+    val z = ofType[InSeq]
+  }
+}
-- 
cgit v1.2.3